The present invention relates to an apparatus and method for projecting light in two orthogonal planes and, more particulary, to such an apparatus and method in which reference planes of light are provided for use in laying out a construction site, or the like.
Laser beam systems have been employed in numerous surveying and construction applications. In one such system a laser beam projector provides a rotating laser beam which establishes a reference plane. In use, the projector may, for example, be mounted at the desired height of a hanging ceiling in a building under construction. The beam is rotated in a horizontal plane to assist the workers in determining the proper height for the ceiling throughout the room. The rotating laser beam provides a continuous, visible plane of light that creates a constant horizontal bench mark of elevation over the entire work area.
Typically, the laser projector of this type can also be positioned to provide a vertical reference plane of light, or a plane of light in other orientations. A laser projector can be used in this manner for laying out overhead drop walls and bulkheads, and in other construction operations. U.S. Pat. No. 4,062,634, issued Dec. 13, 1977, to Rando et al; U.S. Pat. No. 4,035,084, issued July 12, 1977, to Ramsay; and U.S. Pat. No. 4,031,629, issued June 28, 1977, to Paluck, all disclose rotating laser beam devices.
An improved rotating beam projector is disclosed and claimed in U.S. Pat. No. 4,676,598, issued June 30, 1987, to Markley et al. The Markley et al projector produces a stationary reference beam, as well as a moving reference beam. The moving reference beam is normal to the stationary reference beam and rotates about an axis which is aligned with the stationary reference beam. The moving beam thus defines a reference plane, while the stationary beam defines a reference line which is perpendicular to the reference plane. In using such a device, the plane defined by the rotating beam may be aligned with a building structure, for example a wall, and the stationary beam then provides a reference line which is normal to the wall.
While the Markley et al projector provides substantial improvements over earlier laser beam projection systems in that a line and a plane can be defined simultaneously by the projected laser beams, nevertheless a need exists for a laser beam projection system more suited for facilitating the layout of a reference grid. More specifically, a need exists for a beam projection device which is capable of simultaneously projecting a pair of substantially orthogonal beams of laser light which each diverge into thin, fan beams of light in generally vertical planes.
Such fan beams effectively provide a pair of perpendicular planes of light which may be easily sensed by an appropriate sensor positioned in the planes at any height. Additionally, such a beam projection device may be positioned at a corner of the desired reference grid and aligned to project one plane of light along a desired base line. When the device is aligned in this manner, the second, orthogonal plane of light defines a side line of the grid. Sensors may be used to determine the location of the second plane of light and, therefore, the side line. Cross points of the reference grid may be determined by measuring distances along the base and side lines, and the process may be repeated at other corners of the grid.
It is seen that there is a need, therefore, for a laser beam projection apparatus and method in which the lay out of a reference grid is facilitated and in which light is projected in two orthogonal planes to provide reference planes of light.